Various radio communication systems that operate in accordance with 3GPP (Third Generation Partnership Project) protocols have been used. In radio communication systems that operate in accordance with LTE/SAE (Long Term Evolution/System Architecture Evolution) protocols specified by 3GPP, a logical communication path (a user-plane path) used for communicating user data is established in accordance with control by a switching center (Mobility Management Entity (MME)). The path of the established user-plane path can be switched in accordance with the control by the switching center. The control of the user-plane path described above is performed through a logical communication path (a control-plane path) used for communicating control data.
In the radio communication systems that operate in accordance with the conventional LTE protocols, an eNB (evolved Node B) is used as a radio base station that can communicate directly with a user device by radio. The eNB has a control-plane path to a switching center, to other eNB, and to a user device. When the user device newly starts communicating user data, the eNB, in accordance with a control message transmitted from the switching center through the control-plane path, operates so as to establish a user-plane path for the user device to use. The eNB to which the user device is currently connected exchanges, when the user device moves to a cell formed by another eNB, control messages with the user device and with the other eNB through control-plane paths so as to cause the user device to be handed over to the other eNB.